Phase‐Field Modeling of Electromechanical Breakdown in Multilayer Ceramic Capacitors

Abstract

Multilayer ceramic capacitors (MLCCs) are drawing increasing attention in the application of energy storage devices due to their high volumetric capacitance and improved energy density. However, electromechanical breakdown always occurs, especially under high operation voltage, which limits their application in high‐voltage circuit. In this work, a phase‐field electromechanical breakdown model is developed to give a fundamental understanding on the coupled electromechanical effect on the dielectric breakdown of MLCCs. The thickness‐dependent dielectric breakdown strength is well simulated through this phase‐field model. It is found that the dielectric breakdown strength and the patterns of final breakdown path is significantly influenced by the defect concentration and applied stress. An enhanced breakdown strength of MLCC is proved under either compressive or shear stress state. The model not only provides a mechanistic understanding toward the electromechanical breakdown in MLCCs, but also applies to all kinds of dielectrics and serves as guidance toward the design of high‐voltage dielectrics.

Perspectives and challenges for lead-free energy-storage multilayer ceramic capacitors

“…The thickness of dielectrics has a significant effect on E b because of the fewer defects in thinner dielectric layer. The E b exponentially increases as the thickness (t) of the single dielectric layer decreases [12,[14][15][16][17], and it roughly follows this relationship:…”

“…At the mesoscopic scale, a phase-field electromechanical breakdown model was developed in our previous work to simulate the dielectric breakdown behavior in MLCCs [120][121][122]. The final patterns of the breakdown path inside MLCCs with various margin lengths are shown in Figs.…”

Improving the comprehensive energy storage performance of composite materials through the coupling effect of AgNbO3/PVDF nanocomposite

“…A theoretical model was built through Equations 5-7 into COMSOL Multiphysics. [64][65][66][67][68][69][70] We consider that as the weight percentage rises, the density of AgNbO 3 ultrafine powder in the composite material also increases. The growth process of electrical trees and the electric field distribution of AgNbO 3 /PVDF composites with different weight contents is shown in Figure 7A, where S 1 to S 3 represent models with increasing weight contents.…”

“…The symbols with over‐bars are the dimensionless counterparts of the corresponding quantities. A theoretical model was built through Equations into COMSOL Multiphysics 64–70 …”

Effects of Nanofibers Orientation and Aspect Ratio on Dielectric Properties of Nanocomposites: A Phase-Field Simulation

“…However, in practical applications, dielectric materials with both high E b and ε r are in great demand. Different from the vast majority of intrinsic polymer and inorganic ceramic capacitors, organic–inorganic nanocomposite dielectrics promise to combine the advantages of both and to have the potential to simultaneously lead to high E b and ε r , and they are expected to achieve high U rec dielectric capacitors for high pulse power systems and future dielectric energy storage. − There are already numerous studies on organic–inorganic composite dielectric materials, and their energy storage is significantly affected by the properties of the polymer, the inorganic filler particles, and the interaction between them. − Among these investigations, nanofiber-filled composites with high aspect ratios have received more attention owing to their higher interfacial polarization, leading to higher ε r . − There are also experimental and numerical simulation studies showing that the E b of the composites are deeply affected by the filling of the nanofibers. − However, due to the complexity of the experiment, there are few studies on the effect of the specific ideal orientation angle of the nanofibers regarding the E b and dielectric response of the nanocomposites. , Furthermore, many numerical simulation studies have only studied the effect of fiber horizontal and vertical orientation regarding the dielectric performances of nanocomposites. , In the numerical simulations, the phase-field method can intuitively characterize the breakdown path of composite materials, quantitatively study the influence of various factors, and achieve good results. ,− Pitike and Hong developed a phase-field model to investigate breakage generation and spread during breakdown of solid dielectrics and subsequently applied this approach to the breakdown behavior of composite dielectrics. , By introducing nonlinear ferroelectric fillers, Cai et al further developed this method to quantitatively study the breakdown and dielectric properties of various structural composites. , Therefore, it would be very interesting to study the effects of specific orientation and aspect ratio of nanofibrous fillers regarding the breakdown and dielectric properties of nanocomposites by the phase-field method.…”